Pronounced vasodilation of the maternal vasculature occurs during normal pregnancy. Also, pressor responsiveness & vascular reactivity to infused vasoconstrictors are attenuated. These cardiovascular changes ultimately assure the adequate delivery of oxygen & nutrients to the fetus. A successful outcome in preventing rejection of the fetoplacental semi-allograft. Insight into the mechanisms underlying these adaptions of normal pregnancy is particularly critical because in preeclampsia.